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Carbon partitioning and rhizosphere C‐flow in Lolium perenne as affected by CO 2 concentration, irradiance and below‐ground conditions
Author(s) -
Paterson EriC.,
Hodge Angela,
Thornton Barry,
Millard Peter,
Killham KeN.
Publication year - 1999
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1046/j.1365-2486.1999.00267.x
Subject(s) - lolium perenne , loam , rhizosphere , microcosm , chemistry , dry matter , flux (metallurgy) , photon flux , agronomy , environmental chemistry , shoot , organic matter , horticulture , zoology , environmental science , soil water , soil science , poaceae , biology , photon , genetics , physics , organic chemistry , quantum mechanics , bacteria
Summary Plant responses to increasing atmospheric CO 2 concentrations have received considerable interest. However, major uncertainties in relation to interactive effects of CO 2 with above‐ and below‐ground conditions remain. This microcosm study investigated the impacts of CO 2 concentration on plant growth, dry matter partitioning and rhizodeposition as affected by: (i) photon flux density (PFD), and (ii) growth matrix. Plants were grown in a sandy loam soil for 28 d under two photon flux densities: 350 (low PFD) and 1000 μmol m –2 s –1 (high PFD) and two CO 2 concentrations: 450 (low CO 2 ) and 720 μmol mol –1 (high CO 2 ). Partitioning of recent assimilate amongst plant and rhizosphere C‐pools was determined by use of 14 CO 2 pulse‐labelling. In treatments with high PFD and/or high CO 2 , significant ( P < 0.05) increases in dry matter production were found in comparison with the low PFD/low CO 2 treatment. In addition, significant ( P < 0.05) reductions in shoot %N and SLA were found in treatments imposing high PFD and/or high CO 2 . Root weight ratio (RWR) was unaffected by CO 2 concentration, however, partitioning of 14 C to below ground pools was significantly ( P < 0.05) increased. In a separate study, L. perenne was grown for 28 d in microcosms percolated with nutrient solution, in either a sterile sand matrix or nonsterile soil, under high or low CO 2 . Dry matter production was significantly ( P < 0.01) increased for both sand and soil grown seedlings. Dry matter partitioning was affected by matrix type. 14 C‐allocation below ground was increased for sand grown plants. Rhizodeposition was affected by CO 2 concentration for growth in each matrix, but was increased for plants grown in the soil matrix, and decreased for those in sand. The results illustrate that plant responses to CO 2 are potentially affected by (i) PFD, and (ii) by feedbacks from the growth matrix. Such feedbacks are discussed in relation to soil nutrient status and interactions with the rhizosphere microbial biomass.